Electron tube system



A ril 10, 1934. a. J. KELLEY ELECTRON TUBE SYSTEM Filed May 12, 1930 5Sheets-Sheet l Flat p 193% G. J. KELLEY 1,954,779

ELECTRON TUBE SYSTEM Filed May 12, 1930 5 Sheets-Sheet 2 April 10, 1934.G. J. KELLEY 1,954,779

ELECTRON TUBE SYSTEM Filed May 12, 1930 5 Sheets-Sheet 3 p Svvoemtoz 6/6278/1/60 J fizzzff April 10, 1934. 5 KELLEY 1,954,779

ELECTRON TUBE SYSTEM April 1934- G. J. KELLEY 1,954,779

ELECTRON TUBE SYSTEM Filed May 12, 1930 5 Sheets-Sheet 5 W/ r/vass WOW?E %%%W Patented Apr. l0, 1934 U STATES ELECTRON TUBE SYSTEM DelawareApplication May 12, 1930, Serial No. 451,562

11 Claims.

The present invention relates to electron tube systems, and is acontinuation in part of my copending application Serial No. 429,956,filed February 20, 1930.

An object of my invention is the control of signal current effectswithin a direct coupled tube system so as to produce a high order ofradio or audio frequency amplification throughout the system.

Another object of my invention is to so regu late and apportion thesignal current effects with respect to direct current effects thatabnormally high coefficients of amplification may be obtained, whilemaintaining faithful reproduction of the signals to be amplified.

Other objects of my invention will become apparent as the description ofmy invention is developed with reference to the accompanying .drawingsin which modification of the direct coupled tube system of Fig. 1,

Fig. 4. diagrammatically illustrates a modification of the circuitarrangement of Fig. 3 and involves certain humbucking features,

Fig. 5 diagrammatically illustrates a modification of the energizationsystem of Fig. 1,

Fig. 6 diagrammatically illustrates a modification of the circuitarrangement of Fig. 5,

Fig. 7 diagrammatically illustrates a modification of the energizationand signal current system of Fig. 6,

Fig. 8 diagrammatically illustrates a modification of the energizationand signal current system of Fig. 12 of my copending application hereinbefore referred to,

Fig. 9 diagrammatically illustrates a modification of the circuitarrangement of Fig. 4, and

Fig. 10 diagrammatically illustrates the circuit arrangement of acomplete radio receiving system embodying certain of the featuresdisclosed in my copending application hereinbefore referred to incombination with certain of the features described with reference to theforegoing figures. i

Referring to Fig. l, VT1 and VT2 designate two electron tubes in directcoupled cascade relation having a signal input circuit SI andan outputcircuit which may consist of an output transformer OT and a loudspeaking device LS. or other type of indicator. The input'circult mayconsist of any type of instrumentality developing an alternating currentpotential or fluctuat ing direct current potential.

VT1 and VT2 are four element and three element electron tubesrespectively the cathodes of v which are energized through heatingcurrent transformers HTi and I-ITz. The plate of thetube VTZ isconnected through a filter choke coil FCh to the positive terminal P ofarectifier system including a rectifier tube RT energized from a powertransformer PT. The cathode of tube VT2 is connected through aresistance R to thenegative terminal G of the rectifier system. Theoutput of the rectifier is shunted by a filter condenser F01.

The cathode of tube VT]. is connected to the terminal G through astabilizing resistance SR, the grid and screen grid being returned topoints A and B on the resistance R, all of which structure has beendescribed in detail in my copending application hereinbefore referredto.

In this instance, however, I have provided a filter resistance ERA, inthe grid circuit of tube VT]. which may be shorted out by a switch 53depending upon whether it is desired to have or remove any signalcurrent regeneration within the system.

In the arrangement of Fig.1, I connect the plate of tube'VT1 and thegrid of tube VTz to the terminal P of the rectifier system through acoupling resistance CR and two series resistances R1 and R2. Thecondenser C2 serves both as a filter condenser and as signal currentcondenser for the output circuit of tube VT2. The condenser C3 serves asa filter condenser in conjunction with the resistance R1 completing thesignal input circuit for the tube VT2, and it also completes the signaloutput circuit of tube VTi.

When the switches S1 and S2 are open as shown signal current flowing inthe plate circuit of tube VTl developes signal current potentials acrossboth the resistances CR and R2, the total potential being impressed uponthe input circuit of tube VT2. If now the switch S1 is closed the platecircuit of tube VT1 is closed through the condenser C5. The impedanceinput circuit oftube V'Iz remains the same, however, the resultantaction being similar to a step-down auto-transformer.

'If, however, the switch S2 is closed the plate circuit of the tube VTland the grid-circuit of tube VTz are simultaneously completed throughthe condenser C4, the signal currents in the plate circuitof tube VT].developing potentials only-across the resistance CR and these samepotentials be- "ing applied to the input circuit of tube VTz.

denser C1.

The functions of these condensers are more fully explained withreference to Fig. 2 in which the resistances CR, R2 and R1 of Fig. 1 aredesignated a, b, 0. With the switches S1 and S2 open the signal currentpath from the plate to the cathode of tube VT1 is through resistances,a, b, c, and condensers, C2, RC, and BC. The impedance to signal currentin the input circuit of tube VT2 is the resistance of a, b, c and thecondenser C2.

If the arm of switch S1 is moved across contacts 1, 2, and 3 theimpedance of the coupling between tubes may be changed. When on contact1 the impedance of the condenser C is substituted for the impedance ofthe series condensers RC and BC in the plate circuit of tube VT1. Whenthe arm of switch S1 is moved to contact 2 the impedance of the section0 is removed, thus reducing the coupling between tubes to that of thesections a and b. When the arm of switch S1 is moved to contact 3 thesection a is the only coupling between tubes VT1 and VTz. The condenserC acts simultaneously to reduce the impedance in both the output circuitof thetube VT1 and the input circuit of tube VT2 because the combinationof condensers BCand RC maintains the cathode of tubes VT1 and VT2 atsubstantially the same signal current potential. However, if eithercondenser BC or RC has substantial impedance to signal currents acondenser C1 and switch S2 must be provided if it is desired to equalizethe signal current impedance in the two circuits.

Referring to Fig. 3, I have modified the circuit arrangement of Fig. 1to include a tube VT1.

Herein I have shown the cathode of tube VT'1 connected to the terminal Gof the source SF through a bias resistance Br, the grid of this tubebeing returned to the point A on the resistance R which is shunted tothe cathode through a con- The plate of tube VT1 and the grid of tubeVT1 are returned to a point A on the resistance R. For the tube VT1 Ihave also provided a hum bucking condenser HBO connected between thecathode and the variable tap D on the resistance R.

In Fig. 4 I have modified the circuit arrangement of Fig. 3 to utilize ascreen-grid tube VT1. Herein I have returned the grid of tube VT1 to apoint A on a resistance R7, the resistance R1 being of a very high valueand functioning in conjunction with the condenser C1 as a filterresistance similar to the function of the resistance FRl of Fig. 1. Thescreen grid of tube VT1, I have returned to the point E on theresistance R through a filter resistance FR3 which is shunted to thecathode by means of a filter condenser F03. The plate of tube VT1 andthe grid of tube VT, I have connected to the terminal P of the source SFthrough a radio frequency choke coil RCh, a coupling resistance CR1 andresistances R3, R2 and R1, the junction between the resistances CR1 andR3 being shunted to ground by the condenser C5.

In the input circuit of tube VT2 I have made the following change. Theplate of tube VT1 and the grid of tube VT2 I have connected to theterminal P of the source SF through the resistances R2 and R1, and havealso connected the plate of tube VT1 and the grid of tube VT2 to thecenter-tap of the filament of the tube VTz through a resistance CR. Inother respects the connections are the same as in the circuitarrangement of Fig. 3.

In operating with this change of connection in the grid circuit of tubeVTz I obtain a remarkable phenomenon which has the. effect of'substantially doubling the effective output ability (wattage) of thesystem over that normally understood to be possessed thereby. Forexample, in using a Well-known commercial power amplifier tube at VTzrated to give about 1 watts of undistorted output with specified ratedenergizing potentials, I find that with the same rated potentials andthe special connections of Fig. 4, I obtain undistorted output energy atthe rate of substantially 3 watts.

In Fig. 5 I have shown the feature of filtration of the screen gridcircuit as applied to the tube VT1 of the circuit arrangement of Fig. 1.Herein I have shown the screen grid of tube VT1 energized through thefilter resistance FR3 from the potential developed across the resistanceR. The value of the resistance FR: is dependent upon the point along theresistance R from which the potential is taken for the screen grid. Thescreen grid is shunted either to ground or to the cathode of the tubeVT1 by means of a condenser C, the only change noticeable in theoperation required being a shifting of the point D on the resistance Rto which the hum bucking condenser HBO is returned.

In Fig. 6 I have shown a modification of the circuit arrangement of Fig.5 wherein I have employed a grid filter comprising filter resistance FRland filter condenser F04, a screen-grid filter comprising filterresistance F133 and condenser FCa; I have further utilized the chokingaction of the speaker field winding SW in conjunction with the condenserRC to filter hum from the resistance R. I have found that the connectionof the condenser C4 from the junction between the resistances CR and R1and the cathode of tube VT1 serves to adequately reduce the hum of thesystem to a value below audibility without the use of the hum buckingcondenser HBC described with reference to the foregoing figures.

In Fig. 7 I have shown a peculiar utilization of a feature of thecircuit arrangement of Fig. 5. If the by-pass condenser I-IBC of Fig. 5is omitted there will develop a signal current potential across thestabilizing resistance SR so that the grid of tube VTa may be directlyconnected to the cathode of the tube VT1, the plate thereof beingconnected to the terminal P of the source SF, the resistance SR servingas the coupling resistance between tubes VT1 and VT2.

In Fig. 8 I have shown the feature of the combination of resistances CR,R2, R1 and the condenser C3 incorporated in a two tube direct coupledsystem. The effect of this combination in the output wattage of a twotube system as shown in this figure is even more noticeable than whenutilized in the three tube system, the operation of which was describedwith reference to Fig. 4.

In Fig. 9 I have shown the circuit arrangement of Fig. 4 modified insuch a manner that tube VT1 functions primarily as a radio frequencyamplifier, the input for the system comprising a tunable transfercircuit T1 energized from an Antenna Ant, through a volume controlsystem comprising an antenna resistance and a condenser Cs. In thisarrangement I have replaced the radio frequency choke coil RCh of Fig. 4

-with a tunable circuit T2 comprising an inductance L2 and a variablecondenser VCz connected in the manner shown, and have connected thecondenser C5 between the junction between the inductance L2 and ground.In this arrangement the bias for the tube VT1 is determined by .the

proportioning of the resistances SR, CR, R3, R2,

, and R1 as in the arrangement of Fig. l. The

signal input for tube VTr however isdetermined by the impedance of thetuned circuit T2 to cur rents of signal frequency, the input circuit tothe cathode of tube V T1 being closed through a condenser C6. Thevariable connection between the plate of tube VTi and the inductance L2functions in the same manner as the variable tap on an auto-transformerto vary the coupling between the tubes VT1 and VT1. Between the plate oftube VTz and the cathode I have connected a radio frequency by passcondenser RFC to shunt radio frequency currents away from the outputtransformer OT. This condenser, while helpful, is not essential to theoperation of the circuit arrangement illustrated in this figure.

In Fig. 10, I have shown a direct coupled tube system functioning as aradio frequency amplifier system and a direct coupled tube systemfunctioning as a detector amplifier system connected in cascade andenergized from a common source of fluctuating unidirectional current SF.Across the terminals P and G of the source SF I have connected theprimary of the output transformer OT, the anode to cathode path of tubeVTz and the resistance R. In shunt to the anode to cathode path of tubeVTz I have connected two high resistances R1 and R2, and have energizedthe grid of tube VTz and the plate of tube VTl by connecting the samethrough the coupling resistance CE. The tube VT1 is otherwise energizedin the manner described with reference to the foregoing figures, thetunable 1 input circuit T1 thereof being provided with a filter s" stemincluding filter resistance F334 and filter condenser FC4 as previouslydescribed with reference to Fig. 6 hereof. I

Across the terminals G and P of the source SF I have connected apotentiometer R from which I have energized a four stage direct coupledtube system VT1, VT2, VT1, VT2 by connecting the cathode of tube VTi tothe terminal G of the source SF through a stabilizing resistance SR1which is shunted by a signal current condenser Ci, andconnecting thecathodes of tubes VT'z, VT1, VT2 and directly to the points G2, G3 andG4 of the potentiometer R, each of these points being by-passed toground by condensers B01, BCz B03 respectively, and the remainingelectrodes as follows: The grid of tube VT'i is connected through atunable input circuit, such as a loop LP, to the point A1 on theresistance B, the resultant voltages between the cathode of tube VT'1and the point A1 on the resistance R. stabilizes the four tube directcoupled system in the same manner as the voltages between the cathode oftube VTl and the point A on the resistance R stabilize the two tubedirect coupled system as has been described in detail with reference toFig. 5 in my copending application hereinbefore referred to. The screengrids of tubes VT'1, VTz, VT1 and VT2 are respec-' tively connected topoints B1, B2, B3 and B4 on the potentiometer R of proper voltage withrespect to the points G, G2, G3 and G4. The plate of tube VTi and thegrid of tube VT'z are returned to the point A2 on the potentiometer Bthrough th coupling resistance CR1. The plate of tube VT2 and the gridof tube VT"1 are returned to the point As on the potentiometer B througha coupling circuit including inductance L2, condenser V02, resistanceCR2 and condenser Co as hereinbefore described with reference to "'1;Fig. 9. The plate of tube VT1 and the grid of tube V'I"2 are connectedto the point Al on the potentiometer R. The plate of tube VT2 isconnected to the terminal P of the source SF through a plate resistancePR, and coupled to the grid of tube VT1 through a coupling condenser CC.

The operation of this circuit arrangement is as follows: The inputcircuit LP selectively impresses signal currents voltages upon the gridof tube VTi.

The tube VT'1 amplifies these signals and aperiodically impresses themon the grid circuit of tube VTz by means of the coupling resistance CR1.The tube VT'z further amplifies the signals and selectively impressesthem on the grid circuit of tube VT1 through the tuned circuit T2. Thetube VT1 further amplifies these signals and aperiodically impressesthem on the grid circuit of tube VT"2 by means of the couplingresistance CR3. The tube VT"2 further amplifies the signals and developssignal current potentials across the resistance PR. which po tentialsare resonantly abstracted from this resistance by the tuned circuit T1coupled thereto through the condenser CC. The tubes VT1 and VT2 thendetect and amplify the amplified high frequency currents in the mannerfully set forth in copending application of Sidney Y. White, Serial No.318,754, filed July 29, 1929.

While I have illustrated and described my invention as embodied incertain specific circuit arrangements it is to be understood thatvarious modifications thereof may be made without departing from thespirit of my invention as defined by the claims appended hereto.

Having thus described my invention, what I claim is:

1. In an electron tube system, the combination of a plurality ofelectron tubes direct coupled in cascade through a common impedanceelement and means for varying the effective value of said impedance withrespect to signal currents while maintaining the value of said impedanceconstant with respect to direct currents flowing therethrough, saidmeans consisting of a condenser variably connected between selectedpoints on said impedance and the cathode of one of said tubes.

2. In an electron tube system, the combination of a plurality ofelectron tubes direct coupled in 1.

cascade through a common impedance element and means for varying theeffective value of said impedance with respect to signal currents whilemaintaining the value of said impedance constant with respect to directcurrents flowing therethrough, said means consisting of a condenservariably connected between selected points on said impedance and thecathode of the tube containing said impedance within its plate circuit.

3. In an electron tube system, the combination 1,

of a plruality of electron tubes direct coupled in cascade through acommon impedance element and means for varying the effective value ofsaid impedance with respect to signal currents while maintaining thevalue of said impedance constant with respect to direct currents flowingtherethrough, said means consisting of a condenser variably connectedbetween selected points on said impedance and the cathode of the tubecontaining said impedance within its grid circuit.

4:. In an electron tube system, the combination of a plurality ofelectron tubes direct coupled in cascade through a common impedanceelement and means for varying the eifective Value of said impedance withrespect to signal currents while maintaining the value of said impedanceconstant with respect-to direct currents flowing therethrough, saidmeans consisting of condensers variably connected between selectedpoints on said impedance and the cathodes of each of the tubescontaining said impedance within their circuits.

5. In an electron tube system, the combination of a plurality of tubesdirect coupled in cascade, a source of current for energizing theelectrodes of said tubes, a common. impedance element through which theplate-circuit of one tube and the grid circuit of another tube areenergized and a high resistance element connectedflbetween the grid andcathode of said other tube.

6. In an electron tube system, the combination of a plurality ofelectron tubes direct coupled in cascade, the coupling element betweentwo tubes comprising a plurality of energy transfer elements one ofwhich hashigh impedance to high frequency currents and low impedance tolow frequency currents and another of whichhas high but substantiallylike impedance for currents of both frequencies.

'7. In an electron tube system, the combination of a plurality ofelectron tubes direct coupled in cascade, the coupling element betweentwo tubes comprising a tunable circuit and a high impedance ofsubstantially constant value to low frequency currents.

8. In an electron tube system, the combination of a plurality ofelectron tubes direct coupled in cascade, the coupling element betweentwo tubes comprising a tunable circuit and a high inipedance ofsubstantially constant value to low frequency currents and means forshunting high frequency currents around said last mentioned impedance.

9. In an electron tube signal transfer system including a source offluctuating unidirectional potential, means and connections forenergizing tube electrodes of said system, and an electron dischargetube having'the average potential difference between its cathode andcontrol electrode differentially determined by two potential developingelements one of which is disposed for energization by discharge currentof said same tube and the other of which is disposed for energizationpredominantly at least by discharge current of another tube of saidsystem, the combination therewith of a condensive-resistive impedancehaving its resistive element arranged between said cathode and controlelectrode for lowering the potential of said controlelectrode under theinfluence of space charge current therethrough and having both itselements so arranged as to divert from said two potential developingmeans fluctuating components of said source.

10. In an electron tube signal transfer system including a source offluctuating unidirectional potential, means and connections forenergizing tube electrodes of said system, and a screen-grid electrondischarge tube having the average potential difference between itscathode and control electrode differentially determined by two potentialdeveloping elements one of which is disposed for energization bydischarge current of said same tube and the other of which is disposedfor energization predominantly at least by discharge current of anothertube of said system, the combination therewith of a resistive element inthe screen-grid connection of said screen-grid tube, and a condenserdisposed between said resistive element and a potential point in saidtwo potential developing elements, whereby fluctuat- 195 ing componentsof said source are diverted from said screen grid and the potential ofsaid screen grid is lowered under the influence of space currenttherethrough.

11. In an electric signal transfer system including two electrondischarge tubes, a source of potential, and means for energizing tubeelectrodes of said system from said source, the combination of apotential developing means common to the cathode-anode andcathode-control electrode circuit of the one of said two tubes, and aconnection between a point in said potential developing means and thecontrol electrode of the other of said two tubes, whereby through saidconnection signal energy is transferred from said one tube to said othertube.

GERARD J. KELLEY.

